Wound care What are the types of skin graft?
Split skin graft – This type of skin graft is taken by shaving the surface layers (epidermis and a variable thickness of dermis) of the skin with a large knife called a dermatome. The shaved piece of skin is then applied to the wound. This type of skin graft is often taken from the leg. A split skin graft is often used after excision of a lesion on the lower leg.
Full thickness skin graft – This type of skin graft is taken by removing all the layers of the skin with a scalpel (a Wolfe graft). It is done in a similar way to skin excision. The piece of skin is cut into the correct shape, then applied to the wound. This type of skin graft is often taken from the arm, neck or behind the ear. It is often
used after excisions on the hand or face. Source: DermNet NZ
two decades,” remarks Guangyu Bao, a PhD researcher in the department of mechanical engineering. “However, they suffer from small pore size and low mechanical toughness. The former limits the nutrients from reaching deep into the biomaterials and inhibits cell growth. The latter restricts the use of existing biomaterials for repairing mechanically active tissues. Our material overcomes these two challenges simultaneously for the first time.”
“Many injectable biomaterials, mostly hydrogels, have been developed for tissue
repair over the last two decades.” Guangyu Bao
The new biomaterial has a large pore size – around 100 to 1,000 times larger than most existing hydrogels – and is around eight to 40 times tougher than the standard. “Generating large pores is very difficult for injectable hydrogels,” says Bao. “To this end, we used a pore-forming polymer called chitosan, which is derived from crustaceans, to create large pores. To make the porous hydrogel tough and stable, we infused it with another elastic polymer to reinforce the mechanical performance.” The upshot is that the resulting material is mechanically stable even when exposed to the
An illustration of skin transplantation using a technologically advanced skin graft treatment.
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harshest conditions in the human body. It was tested in a machine designed to simulate the human vocal cords, which vibrate at 120 times a second. Unlike standard hydrogels, the new material stayed intact under the duress. If injected into the human body, the material would first provide physical support to the wounds, preventing further damage. It would then recruit cells from the surrounding tissues to remodel the wound as time goes by. Over time, the material would degrade, eventually being replaced entirely by the new tissue. Like Smith’s material, Bao’s is in an early stage of development, but could have exciting applications further down the line. “We will be testing our hydrogel in animals very soon,” says Bao. “We will first investigate the biocompatibility and biodegradation of our hydrogel in rat models. Later, we will be working with surgeons on vocal cord repair in rabbit models. “If the results are promising, we will apply for clinical trials. At the same time, we are also looking into how it works for skin wound repair. We welcome collaborations with healthcare professionals to accelerate the process of moving our biomaterials for clinical trials.” It is important to note that these kinds of technologies could have applications beyond wound healing. Smith says that his technology could be used as an in vitro skin model for studying disease, or as a platform for drug screening. Bao’s could be used within drug delivery and tissue engineering – and the team is even looking to use the hydrogel to create lungs for testing out Covid-19 drugs. Wound healing, however, would be the priority. While conceding that it is a little early to speculate, Smith believes the patients most likely to benefit from his team’s technology would be those with severe trauma and deep necrotic wounds. In these instances, it could mean the difference between healing and having to amputate the affected limb. “We were able to demonstrate a degree of integration of the surrounding tissue into the hypodermal layer of the bioprinted skin in a relatively short period of time,” says Smith. “This mobilisation of tissue and rapid integration is particularly important, especially within deep wound repair.” For the time being, these kinds of artificial skin grafts are some way from being applied in the clinic. Over time, however, biomaterials engineering could open up new avenues in the care and treatment of chronic wounds, significantly reducing the burden on individuals and healthcare systems, and giving hope to those who suffer from chronic wounds where there was none before.
Practical Patient Care /
www.practical-patient-care.com
Artemida-psy/
Shutterstock.com
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